U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Datums Page Page 1 of 5 Station ID: 8666775 PUBLICATION DATE: 05/06/2003 Name: LEADENWAH CREEK SC NOAA Chart: 11522 Latitude: 32° 38.2' N ( 32.63670) USGS Quad: WADMALAW ISLAND Longitude: 80° 12.1' W ( -80.20170) To reach the tidal bench marks from the intersection of U.S. Highway 17 and State Highway 20 west of Charleston, proceed south on State Highway 20 for 10.3 km (6.4 mi) to State Highway 700, turn right and go SW on State Highway 700 for 13.8 km (8.6 mi) to Edith L. Frierson Elementary School, turn right onto a dirt road and go 2 km (1 mi) to a three-way split in the road, bear left and go 0.5 km (0.3 mi) to another intersection, bear left and go 0.2 km (0.1 mi) to the driveway of Johnson's residence, turn right and go another 0.2 km (0.1 mi) to the main house. The bench marks are along to driveway and at Johnson's pier. The tide gauge and staff were on Johnson's pier and on Dr. Pratt and Thomas' pier to the north after 11/18/77. T I D A L B E N C H M A R K S PRIMARY BENCH MARK STAMPING: 6775 A 1977 DESIGNATION: 866 6775 A TIDAL MONUMENTATION: Tidal Station disk VM#: 6655 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 32° 38.2' N ( 32.63670) LONGITUDE: 80° 12.1' W ( -80.20170) The primary bench mark is a disk crimped to a copper-clad steel rod, located between Johnson's residence and the pier, 15.33 m (50.3 ft) west of the SW corner of the house, 12 m (41 ft) south of a lone oak tree at the bluff, and 10.91 m (35.8 ft) ESE of the centerline of the south end of the wooden catwalk leading to the pier. The bench mark is level with the ground, crimped to a copper-clad steel rod driven 12 m (40 ft) to refusal, and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 2 of 5 Station ID: 8666775 PUBLICATION DATE: 05/06/2003 Name: LEADENWAH CREEK SC NOAA Chart: 11522 Latitude: 32° 38.2' N ( 32.63670) USGS Quad: WADMALAW ISLAND Longitude: 80° 12.1' W ( -80.20170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 6775 B 1977 DESIGNATION: 866 6775 B TIDAL MONUMENTATION: Tidal Station disk VM#: 6656 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Concrete monument OPUS PID: LATITUDE: 32° 38.2' N ( 32.63670) LONGITUDE: 80° 12.1' W ( -80.20170) The bench mark is a disk set in a concrete monument along the driveway leading to Johnson's residence, 23.56 m (77.3 ft) SSE of the east corner of the brick porch at the shed, m (12 ft) NNE of the centerline of the driveway, 0.76 m (2.5 ft) ESE of power pole #33 SE 88D, and level with the ground. BENCH MARK STAMPING: 6775 C 1977 DESIGNATION: 866 6775 C TIDAL MONUMENTATION: Tidal Station disk VM#: 6700 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 32° 38.2' N ( 32.63670) LONGITUDE: 80° 12.1' W ( -80.20170) The bench mark is a disk crimped to a copper-clad steel rod, located along the driveway near the tennis court, 18.41 m (60.4 ft) NE of the center of the tennis court, 18.17 m (59.6 ft) south of the centerline of the driveway, 9.91 m (32.5 ft) south of NW corner of the shed, and 0.46 m (1.5 ft) ENE of the NE corner of the chainlink backstop fence. The bench mark is level with the ground, crimped to a copper-clad steel rod driven 10 m (32 ft) to refusal, and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 3 of 5 Station ID: 8666775 PUBLICATION DATE: 05/06/2003 Name: LEADENWAH CREEK SC NOAA Chart: 11522 Latitude: 32° 38.2' N ( 32.63670) USGS Quad: WADMALAW ISLAND Longitude: 80° 12.1' W ( -80.20170) T I D A L B E N C H M A R K S BENCH MARK STAMPING: 6775 D 1977 DESIGNATION: 866 6775 D TIDAL MONUMENTATION: Tidal Station disk VM#: 6701 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Driveway OPUS PID: LATITUDE: 32° 38.2' N ( 32.63670) LONGITUDE: 80° 12.1' W ( -80.20170) The bench mark is a disk on the south side of the driveway between the entrance and the tennis court, 54.07 m (177.4 ft) SSE of the SE corner of the backstop, 8.14 m 26.7 ft) west of the centerline of the driveway, 2.35 m (7.7 ft) SSE of a three forked oak tree, and level with the ground. BENCH MARK STAMPING: 6775 E 1977 DESIGNATION: 866 6775 E TIDAL MONUMENTATION: Tidal Station disk VM#: 6702 AGENCY: National Ocean Survey (NOS) IDB PID#: SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID: LATITUDE: 32° 38.2' N ( 32.63670) LONGITUDE: 80° 12.1' W ( -80.20170) The bench mark is a disk crimped to a copper-clad steel rod, located at the entrance of the driveway leading to Johnson's residence, 15 m (48 ft) SSW of a 1.37 m (4.5 ft) diameter oak tree, 7.71 m (25.3 ft) NNW of the centerline of the main road, 5.12 m (16.8 ft) WSW of the centerline of the driveway, and 1.07 m (3.5 ft) NW of a mailbox. The bench mark is level with the ground, crimped to a copper-clad steel rod driven 11 m (36 ft) to refusal, and encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 4 of 5 Station ID: 8666775 PUBLICATION DATE: 05/06/2003 Name: LEADENWAH CREEK SC NOAA Chart: 11522 Latitude: 32° 38.2' N ( 32.63670) USGS Quad: WADMALAW ISLAND Longitude: 80° 12.1' W ( -80.20170) T I D A L D A T U M S Tidal datums at LEADENWAH CREEK based on: LENGTH OF SERIES: 11 MONTHS TIME PERIOD: December 1977 - October 1978 TIDAL EPOCH: 1983-2001 CONTROL TIDE STATION: 8665530 CHARLESTON, COOPER RIVER ENTRANCE Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: MEAN HIGHER HIGH WATER MHHW = 2.002 MEAN HIGH WATER MHW = 1.891 MEAN SEA LEVEL MSL = 1.090 MEAN TIDE LEVEL MTL = 0.977 MEAN LOW WATER MLW = 0.064 MEAN LOWER LOW WATER MLLW = 0.000 North American Vertical Datum (NAVD88) Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW 6775 A 1977 4.741 2.850 6775 B 1977 5.093 3.202 6775 C 1977 5.464 3.573 6775 D 1977 6.153 4.262 6775 E 1977 6.086 4.195
U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Ocean Service Page 5 of 5 Station ID: 8666775 PUBLICATION DATE: 05/06/2003 Name: LEADENWAH CREEK SC NOAA Chart: 11522 Latitude: 32° 38.2' N ( 32.63670) USGS Quad: WADMALAW ISLAND Longitude: 80° 12.1' W ( -80.20170) D E F I N I T I O N S Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal Datum Epoch. It pertains to local mean sea level and should not be confused with the fixed datums of North American Vertical Datum of 1988 (NAVD88). NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum constraint adjustment of Canadian/Mexican/United States leveling observations. Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as the single initial constraint. NAVD88 replaces NGVD29 as the national standard geodetic reference for heights. Bench mark elevations relative to NAVD88 are available from NGS through the World Wide Web at National Geodetic Survey. NGVD29 is a fixed datum adopted as a national standard geodetic reference for heights but is now considered superseded. NGVD29 is sometimes referred to as Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological Survey Topographic Quads. NGVD29 was originally derived from a general adjustment of the first-order leveling networks of the U.S. and Canada after holding mean sea level observed at 26 long term tide stations as fixed. Numerous local and wide-spread adjustments have been made since establishment in 1929. Bench mark elevations relative to NGVD29 are available from the National Geodetic Survey (NGS) data base via the World Wide Web at National Geodetic Survey. NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to local MSL and other tidal datums may not be consistent from one location to another. The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique identifiers for bench marks in the tidal and geodetic databases, respectively. Each bench mark in either database has a single, unique VM# and/or PID# assigned. Where both VM# and PID# are indicated, both tidal and geodetic elevations are available for the bench mark listed. The NGS's Integrated Data Base (IDB PID) provides geodetic datum based on traditionally leveled and bluebooked ties to the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/. The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/. The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred to MLLW only when two or more of the bench marks listed have NAVD88 elevations. The NAVD88 elevation relationship shown in the table is derived from an average of several bench mark elevations relative to tide station datum. As a result of this averaging, NAVD88 bench mark elevations computed indirectly from the tidal datums elevation table may differ slightly from NAVD88 elevations listed for each bench mark in the NGS database.